A stronger MRI machine passes safety tests

BioPhotonicsJan 2008
A powerful MRI machine soon may offer physicians a real-time view of metabolic processes in the human brain. As reported in the November issue of the Journal of Magnetic Resonance Imaging, the machine -- installed at the University of Illinois at Chicago -- has succeeded in safety trials on human subjects. Its 9.4-T magnet, from GE Healthcare of Abingdon, UK, has a field strength more than three times that of existing state-of-the-art clinical units. Although the magnet is currently configured for imaging the head, it is large enough to scan the entire body.

With the machine, it may be possible to see, for example, whether small regions within a brain tumor are dying, long before the tumor has begun to shrink, enabling oncologists to provide customized care by better treating each region of the tumor at an earlier stage, when treatment can be more beneficial.

The 9.4-T device permits scientists to visualize different types of molecules, resulting in various views of brain activity. While conventional MRI visualizes water molecules to track biochemical processes, the stronger machine visualizes sodium ions, enabling the tracking of one of the most energy-consuming cellular processes in the brain.

Shown are representative sodium images of the human brain collected using a 9.4-T MRI machine. Reprinted with permission of the Journal of Magnetic Resonance Imaging.The FDA currently classifies MR scanners with a static magnetic field of 8 T or lower as devices that do not pose significant safety risks. The researchers at the university assessed whether exposure to a 9.4-T static magnetic field during sodium imaging at 105.92 MHz affects human vital signs or cognitive function. In the safety trial, 25 healthy subjects were exposed, in random order, to the 9.4-T scanning procedure, as well as to a mock scanning procedure.

Vital signs and cognitive ability were measured before and after both procedures. No significant changes in vital signs such as heart rate, blood pressure or respiratory rate, or in cognitive ability such as memory and sustained attention were found when the subjects were exposed to the magnetic field or to the sodium imaging. Some subjects reported discomfort such as lightheadedness or a metallic taste as they were being moved into the magnetic field.

The researchers are moving toward patient studies of sodium imaging and safety testing for oxygen and phosphorus imaging in humans.